A self contained Iterator from a Map in Groovy

1.groovy

def val = 1
def a = [ hasNext:{ true }, 
          next:{ val++ } ] as Iterator

assert a.take( 2 ).collect() == [ 1, 2 ]

2.groovy

def a = [ val:1,
          hasNext:{ true },
          next:{ this.val++ } ] as Iterator

assert a.take( 2 ).collect() == [ 1, 2 ]

// groovy.lang.MissingPropertyException: No such property: val for class: ConsoleScript1

3.groovy

import java.lang.reflect.Proxy

def a
a = [ val:1,
      hasNext:{ true },
      next:{ Proxy.getInvocationHandler( a ).delegate.val++ } ] as Iterator

assert a.take( 2 ).collect() == [ 1, 2 ]